AC and DC pollution testing methods: accuracy and limitations

Authors: GEORGE Jean-Marie, LEPLEY Damien.
Title: AC AND DC POLLUTION TESTING METHODS: ACCURACY AND LIMITATIONS
Presneted at: 2022 INMR World Congress, Oct 16 – 19 2022, Berlin, Germany.

Abstract

The pollution performance of insulator strings is a center piece in the design of towers for overhead lines. It is even becoming a more pressing question with silicone hydrophobic surfaces which properties are dynamic and respond differently in various service conditions.

The following note gives summarizes some observations and test details which can be of interest in the evaluation of insulator strings in such conditions.

On one side testing hydrophobic surfaces need more work as already engaged in IEC and already summarized in the State of the art of pollution test procedures’ paper*, but the question of heavy and very heavy pollution conditions remains an open question.

More generally speaking it is crucial to avoid over-pessimistic or over-optimistic scenarios through the interpretation of results from a withstand test compared to results from a rapid flashover test.

A particular point of interest is DC where IEC TS 60815-part 4** used data for ceramic insulators which are by far too pessimistic and therefore lead to longer than necessary string designs. It is clearly demonstrated in this document that DC glass insulators (with the appropriate shape for DC applications) outperform largely the USCD expected from the IEC guide.

*Gutman et all: State of the art of pollution test procedures for insulators with Hydrophobicity transfer materials. CSE N°21 June 2021
**IEC/TS 60815-4, “Selection and dimensioning of high-voltage insulators for polluted conditions – Part 4: Insulators for d.c. systems”, Edition 1.0, 2016-10

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